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Pursuing a Level of Reliability

The most important aspect of the plan is determining how much reliability is necessary. You must decide between cost and reliability, probably the most direct tradeoff you will face when planning. Money will buy you more redundancy, better equipment, and more comprehensive coverage. It will not buy you reliability, however, unless your planning and execution are solid.

You must determine how important avoiding downtime is. When your applications are not time sensitive, the cost of downtime is not so severe. So don't make the mistake of overestimating the cost of downtime. High reliability is costly and creates numerous support headaches. If you don't have to go through it, don't. It's also important to remember that the last 10 percent of reliability costs the most.

Another important aspect of planning reliability is to understand what role other factors play in your downtime. Your Internet provider can easily be the source of most of your downtime. No matter how good your system is, it is as good as down if it cannot reach the Internet.

Also consider technical support. Sometimes a problem will be beyond the scope of your in-house technical staff. There are many companies that provide hardware and software support for companies of all sizes. Having your hardware supported means getting a replacement disk or CPU in a matter of hours. Having your software supported means getting immediate answers to critical questions and reducing the time it takes to identify and solve problems.

You also must determine the dollar value of your data. Data is prone to loss, damage, and theft, so plan ahead for these risks. When your data consists mostly of casual e-mail, data loss is not so critical.

Evaluate the necessary security level of your data. That is, how much of the value of the data is lost if an unauthorized user sees it? Everyone uses passwords and file permission structures to secure their data, but do you need more than that? How physically secure is your network? This determination is critical in deciding how secure your transmission must be.

Transmission security means how secure your data is when it moves from place to place. Transmission security is often a weak link that people ignore. When determining the costs and benefits of security measures, never forget to consider the cost of restricted access. Remember that the computer exists so users can access data. If the access to the data is too restricted, you have decreased the value of your whole system. Evaluating and handling security threats are discussed in more detail in Chapters 14 through 16.

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